考虑轮灌方式下的树状管网布局优化问题

Optimization of the Tree-shaped Pipeline Network Layout Based on Rotation Irrigation

农业用水短缺和用水粗放共存,水资源利用率亟待提高。灌溉管道网络是节水灌溉的重要发展趋势,但灌溉管网系统在设计时存在诸多难点。因此,对灌溉工程进行科学合理的规划设计,在满足灌溉需水量和各种液压条件下寻求管网总投资最小的方案,是提高灌溉效率和农业水资源利用率的重要手段。在轮灌方式下的管网布局优化问题中,轮灌组划分方式从根本上决定管网中的流量分布,从而影响管网布置、管网设计和管网总成本。考虑轮灌组容量限制、管道流量流速、工作压力水头等约束,以灌溉系统管道成本和电力成本之和最小作为目标函数,建立了同时考虑灌溉管道网络布置和管网设计的数学模型,并根据模型特点设计一种基于迭代邻域搜索的混合启发式算法进行求解。对一个实际灌溉工程进行优化,设置120、150和190 m^(3)/h三种不同轮灌组容量上限。结果表明,在工作方式方面,由于轮灌组的划分,导致灌溉网络系统工作时的总流量减少,降低管道管径和水源处泵站扬程,从而降低管道成本和电力成本;对于同一算例,灌溉管网的成本也会因轮灌组容量限制不同而存在差异;灌溉系统管道成本和电力成本之间存在效益背反。在管网设计时,需要根据灌区地形和节点分布特点,合理设定轮灌组容量上限和轮灌组划分方式,选择最为经济的管网设计方案。

Agricultural water shortage and extensive water use coexist,and the efficiency of water resources utilization urgently needs to be improved.Irrigation pipeline network is an important development trend of water-saving irrigation,but there are many difficulties in the design of irrigation pipe network system.Therefore,carrying out scientific and reasonable planning and design of irrigation engineering and seeking the scheme with minimum total investment of pipe network under the condition of satisfying irrigation water demand and various hydraulic conditions are important means to improve irrigation efficiency and utilization rate of agricultural water resources.In this paper,considering the constraints such as the capacity limit of the rotation irrigation group,the flow rate of the pipeline and the working pressure water,and taking the minimum sum of the pipeline cost and the power cost of the irrigation system as the objective function,a mathematical model was established which considered both the network layout and the network design of the irrigation pipeline.According to the characteristics of the model,a hybrid heuristic algorithm based on iterative neighborhood search was designed to solve the problem.Meanwhile,an actual irrigation project was optimized,and the upper limits of three different rotation irrigation groups were set,namely 120,150 and 190 m^(3)/h.The results show that in terms of working mode,because of the division of rotation irrigation group,the total flow of the irrigation network system is reduced,and the pipe diameter and the pump station head at the water source are reduced,thus reducing the pipeline cost and power cost.For the same example,the cost of irrigation network will also be different due to the different capacity limits of rotation irrigation group.There is an inverse benefit between the pipe cost and the power cost of irrigation system.In the pipe network design,it is necessary to reasonably set the upper limit of the capacity of the rotation irrigation group and the division method of the rotation irrigation group according to the irrigation area topography and node distribution characteristics,and select the most economical pipe network design scheme.